Wireless IC device component and wireless IC device

ABSTRACT

A wireless IC device includes a wireless IC chip, a coupling electrode, and a radiation plate. The coupling electrode includes coupling portions arranged to be coupled to the wireless IC chip and a pair of opposing ends. The pair of opposing ends are capacitively coupled to each other and oppose the radiation plate to be coupled to the radiation plate. The wireless IC chip uses the radiation plate as an antenna to transmit and receive signals having certain frequencies to and from an RFID system.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to wireless integrated circuit (IC) device components and wireless IC devices. More particularly, the present invention relates to a wireless IC device component and a wireless IC device preferably for use in a Radio Frequency Identification (RFID) system.

2. Description of the Related Art

Hitherto, RFID systems have been developed as article management systems. In such an RFID system, a reader-writer producing an induction electromagnetic-field communicates with an IC chip (also referred to as an IC tag or a wireless IC chip) in a non-contact manner. The IC chip is attached to, for example, an article or a container and stores certain information to be transmitted. The IC chip is coupled to an antenna, that is, a radiation plate to enable communication with the reader-writer.

Japanese Registered Utility Model No. 3148168 discloses a wireless IC device which includes a wireless IC, an annular electrode including a pair of ends, and a matching portion provided on the pair of ends of the annular electrode and in which a dipole radiation plate is connected to a current maximum point of the annular electrode. In the wireless IC device, the wireless IC is coupled to the matching portion and the annular electrode is electromagnetically coupled to the radiation plate. The wireless IC is coupled to the radiation plate via the annular electrode.

In the wireless IC device described above, the use of the annular electrode (coupling electrode) enables the mounting accuracy of the wireless IC to be reduced so as to improve the radiation characteristics. However, such an annular electrode (coupling electrode) has an inductive reactance complementing the impedance and there is a problem in that a long electrical length increases the value of the inductive reactance so as to deteriorate impedance matching between the wireless IC and the radiation plate.

SUMMARY OF THE INVENTION

To overcome the problems described above, preferred embodiments of the present invention provide a wireless IC device component and a wireless IC device that are capable of increasing the electrical length of a coupling electrode and achieving satisfactory impedance matching between a wireless IC and a radiation plate to more satisfactorily couple the coupling electrode to the radiation plate.

A wireless IC device component according to a first preferred embodiment of the present invention preferably includes a wireless IC, and a coupling electrode including at least one coupling portion to be coupled to the wireless IC directly or via a feed circuit and a pair of ends that are capacitively coupled to each other.

A wireless IC device of a second preferred embodiment of the present invention preferably includes a wireless IC, a coupling electrode including at least one coupling portion to be coupled to the wireless IC directly or via a feed circuit and a pair of ends that are capacitively coupled to each other, and a radiation plate coupled to the coupling electrode.

A wireless IC device of a third preferred embodiment of the present invention preferably includes a wireless IC, a coupling electrode including at least one coupling portion to be coupled to the wireless IC directly or via a feed circuit and a pair of opposing ends defined by a cutout of the coupling electrode, and a radiation plate that is opposed to the opposing ends in the coupling electrode so as to be capacitively coupled to the opposing ends.

In the wireless IC device component of the first preferred embodiment and the wireless IC device of the second preferred embodiment, the coupling electrode is preferably defined by an annular electrode via the pair of ends that are capacitively coupled to each other. The coupling electrode has an inductive reactance (XL: jωL) caused by the electrical length and a capacitive reactance (XC: 1/jωC) caused by the pair of ends that are capacitively coupled to each other. Since the inductive reactance has a phase opposite to that of the capacitive reactance, the impedance does not significantly increase because of the increase in the electrical length of the coupling electrode. In other words, it is possible to achieve the impedance matching between the wireless IC and the radiation plate even if the electrical length of the coupling electrode is increased. Specifically, since the paired ends in the coupling electrode are capacitively coupled to each other to provide the capacitive reactance, it is necessary for the coupling electrode to have an increased inductive reactance in order to achieve certain impedance and the electrical length of the coupling electrode is increased. The increased electrical length causes the coupling electrode to receive an increased amount of magnetic field from the radiation plate and, thus, the magnetic coupling between the coupling electrode and the radiation plate is further strengthened.

In the wireless IC device of the third preferred embodiment, the capacitive and magnetic coupling between the coupling electrode and the radiation plate causes the wireless IC to be coupled to the radiation plate so as to establish communication between the wireless IC and an RFID system in a non-contact manner. The coupling electrode has an inductive reactance (XL: jωL) caused by the electrical length and a capacitive reactance (XC: 1/jωC) caused by the coupling electrode and the radiation plate. Since the inductive reactance has a phase opposite to that of the capacitive reactance, the impedance does not significantly increase because of the increase in the electrical length of the coupling electrode. In other words, it is possible to achieve the impedance matching between the wireless IC and the radiation plate even if the electrical length of the coupling electrode is increased. Specifically, since the coupling electrode is capacitively coupled to the radiation plate to provide the capacitive reactance, it is necessary for the coupling electrode to have an increased inductive reactance in order to achieve certain impedance and the electrical length of the coupling electrode is increased. The increased electrical length causes the coupling electrode to receive an increased amount of magnetic field from the radiation plate and, thus, the magnetic coupling between the coupling electrode and the radiation plate is further strengthened.

When the wireless IC is a chip type wireless IC and is directly coupled to the coupling electrode, for example, the coupling electrode preferably performs the impedance matching between the wireless IC chip and the radiation plate. The wireless IC may be indirectly coupled to the coupling electrode via a feed circuit board including a feed circuit, i.e., a resonant circuit and/or a matching circuit. In this case, the feed circuit preferably performs the impedance matching with the wireless IC and the coupling electrode preferably performs the impedance matching between the feed circuit and the radiation plate.

When the coupling electrode is capacitively coupled to the radiation plate via the opposing ends, the mounting accuracy of the coupling electrode in the wireless IC on the radiation plate is not strictly limited. The same applies to the case in which the wireless IC is mounted on the feed circuit board.

In addition, the frequency of a signal used in the communication with a reader-writer is substantially determined by the feed circuit including the resonant circuit and/or the matching circuit which have a certain resonant frequency. The feed circuit is preferably designed in accordance with the impedances of the wireless IC and the radiation plate to be used to adapt to various impedances and to broaden the frequency band in which the impedance matching is enabled. Furthermore, arranging the coupling electrode so that the coupling electrode is coupled to the feed circuit and the radiation plate enables a signal to be efficiently transmitted from the radiation plate via the coupling electrode, so as to improve the radiation characteristics of the signal.

According to various preferred embodiments of the present invention, it is possible to increase the electrical length of the coupling electrode and to achieve satisfactory impedance matching between the wireless IC and the radiation plate. As a result, it is possible to more satisfactorily couple the coupling electrode to the radiation plate.

The above and other elements, features, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing a wireless IC device according to a first preferred embodiment of the present invention.

FIG. 2 schematically illustrates an example of electromagnetic-field distribution in the wireless IC device.

FIGS. 3A and 3B are diagrams showing a wireless IC device component according to a second preferred embodiment of the present invention, where FIG. 3A is a front view and FIG. 3B is a perspective view.

FIG. 4 is a perspective view showing a wireless IC device component according to a third preferred embodiment of the present invention.

FIGS. 5A and 5B are diagrams showing a wireless IC device according to a fourth preferred embodiment of the present invention, where FIG. 5A is a plan view and FIG. 5B is an exploded perspective view.

FIG. 6 is a cross-sectional view showing the main portion of the wireless IC device according to the fourth preferred embodiment of the present invention.

FIG. 7 is a plan view showing a modification of a coupling electrode according to a preferred embodiment of the present invention.

FIG. 8 is an elevation view showing another arrangement of the coupling electrode on a radiation plate.

FIGS. 9A and 9B are diagrams showing a coupling electrode of a wireless IC device according to a fifth preferred embodiment of the present invention, where FIG. 9A is a plan view showing a state in which a feed circuit board is installed and FIG. 9B is a plan view showing a state in which the feed circuit board is removed.

FIG. 10 is an equivalent circuit showing a feed circuit in the wireless IC device according to the fifth preferred embodiment of the present invention.

FIG. 11 is a perspective view showing a state in which a wireless IC chip is installed on the feed circuit board included in the wireless IC device according to the fifth preferred embodiment of the present invention.

FIG. 12 includes plan views showing a layered structure of the feed circuit board.

FIG. 13 is a perspective view of an example in which the coupling electrode is provided on the feed circuit board.

FIG. 14 is a perspective view schematically showing the structure of a wireless IC device according to a sixth preferred embodiment of the present invention.

FIG. 15 is a perspective view showing the wireless IC device according to the sixth preferred embodiment of the present invention.

FIG. 16 is a cross-sectional view showing a modification of the wireless IC device according to a preferred embodiment of the present invention.

FIGS. 17A and 17B are diagrams showing a wireless IC device component according to a seventh preferred embodiment of the present invention, where FIG. 17A is a perspective view and FIG. 17B is a developed view of a coupling electrode.

FIG. 18 is a perspective view showing a wireless IC device component according to an eighth preferred embodiment of the present invention.

FIGS. 19A and 19B are diagrams showing a wireless IC device component according to a ninth preferred embodiment of the present invention, where FIG. 19A is a cross-sectional view and FIG. 19B is a perspective view of a coupling electrode.

FIG. 20 is a cross-sectional view showing a wireless IC device component according to a tenth preferred embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of a wireless IC device component and a wireless IC device according to the present invention will be described with reference to the attached drawings. In the description, the wireless IC device preferably includes a radiation plate and the wireless IC device component is defined as the wireless IC device with the radiation plate being omitted. The radiation plate is preferably provided at the side of an article and the wireless IC device component is coupled to the radiation plate to define the wireless IC device. The same reference numerals are used in the drawings to identify the same or substantially the same components and portions. A duplicated description of such components and portions is omitted herein.

First Preferred Embodiment

A wireless IC device according to a first preferred embodiment of the present invention preferably includes a wireless IC chip 5 arranged to process transmission and reception signals having certain frequencies, a radiation plate 115 provided on a base 110, such as a polyethylene terephthalate (PET) film, for example, and a coupling electrode 125 provided on a base (not shown), such as a PET film, for example, as shown in FIG. 1.

The coupling electrode 125 preferably includes a pair of coupling portions 126 a and 126 b to be coupled to the wireless IC chip 5 and a pair of opposing ends 126 c and 126 d defined by a cutout of the coupling electrode 125. The wireless IC chip 5 preferably includes, for example, a clock circuit, a logic circuit, and a memory circuit. Necessary information is stored in the wireless IC chip 5. A pair of input-output terminal electrodes (not shown) is provided on the rear surface of the wireless IC chip 5. The pair of input-output terminal electrodes is mounted on the pair of coupling portions 126 a and 126 b of the coupling electrode 125 via a conductive adhesive or other suitable adhesive, for example.

The radiation plate 115 preferably includes, for example, a metal laminate made of a conductive material, such as an aluminum foil or a copper foil, that is provided on substantially the entire surface of the base 110. The coupling electrode 125 is preferably arranged so as to be substantially perpendicular to the radiation plate 115 with the opposing ends 126 c and 126 d being opposed to the radiation plate 115. The opposing end 126 c is opposed to the opposing end 126 d so as to be capacitively coupled to the opposing end 126 d, so that the coupling electrode 125 electrically forms an annular electrode. A lower-side portion of the coupling electrode 125 including the opposing ends 126 c and 126 d is capacitively and magnetically coupled to the radiation plate 115. The radiation plate 115 may preferably be provided as a portion of an article, for example, without being combined with the coupling electrode 125 in advance.

Preferably, the coupling electrode 125 has a certain length from the coupling portions 126 a and 126 b to the opposing ends 126 c and 126 d, has a certain resonant frequency corresponding to the electrical length, and also functions as a matching portion arranged to perform phase matching. In addition, the coupling electrode 125 performs impedance matching between the wireless IC chip 5 and the radiation plate 115.

A transmission signal that is sent from the wireless IC chip 5 and that has a certain frequency is transmitted to the radiation plate 115 via the coupling electrode 125, and a signal having a certain frequency is selected by the coupling electrode 125 from signals received by the radiation plate 115 and the selected signal is supplied to the wireless IC chip 5. Accordingly, in the wireless IC device, the wireless IC chip 5 is operated with the signal received by the radiation plate 115 and the response signal from the wireless IC chip 5 is externally radiated from the radiation plate 115.

In the wireless IC device, the capacitive and magnetic coupling between the coupling electrode 125 and the radiation plate 115 causes the wireless IC chip 5 to be coupled to the radiation plate 115 so as to establish communication between the wireless IC chip 5 and an RFID system in a non-contact manner. Energy is transmitted between the coupling electrode 125 and the radiation plate 115 primarily through the magnetic coupling.

In the wireless IC device, the opposing ends 126 c and 126 d of the coupling electrode 125 are opposed to the radiation plate so as to be capacitively coupled to the radiation plate. Such capacitive coupling causes the opposing ends 126 c and 126 d of the coupling electrode 125 to be electrically connected to each other via the radiation plate 115 to electrically form an annular electrode.

The coupling electrode 125 has an inductive reactance (XL: jωL) caused by the electrical length and a capacitive reactance (XC: 1/jωC) caused by the coupling electrode 125 and the radiation plate 115. Since the inductive reactance has a phase opposite to that of the capacitive reactance, the impedance does not significantly increase because of the increase in the electrical length of the coupling electrode 125. In other words, it is possible to achieve the impedance matching between the wireless IC chip 5 and the radiation plate 115 even if the electrical length of the coupling electrode 125 is increased. Thus, the electrical length of the coupling electrode 125 can be increased to strengthen the magnetic coupling between the coupling electrode 125 and the radiation plate 115.

In the first preferred embodiment, the coupling electrode 125 is preferably arranged such that a loop surface of the coupling electrode 125, that is, a surface of the coupling electrode 125 on which the wireless IC chip 5 is disposed, is perpendicular or substantially perpendicular to the radiation plate 115 so as to produce a magnetic field parallel to the radiation plate 115. Consequently, an electric field perpendicular or substantially perpendicular to the radiation plate 115 is produced, a magnetic field is induced by the electric-field loop, and this chain expands the electromagnetic-field distribution. As a result, the wireless IC device is functional even if the wireless IC device is arranged on the metal surface. In addition, it is also possible to cause the metal surface to function as the radiation plate.

FIG. 2 schematically illustrates an example of the electromagnetic-field distribution produced by the coupling electrode 125 (magnetic fields H are indicated by broken lines and electric fields E are indicated by fine lines). The annular coupling electrode 125 functions as a magnetic-field antenna. The coupling electrode 125 causes the magnetic fields H to induce the electric fields E perpendicular or substantially perpendicular to the radiation plate 115, the electric fields E induce the magnetic fields H, and this chain expands the electromagnetic-field distribution. Although the coupling electrode 125 is described as the transmission antenna, the coupling electrode 125 similarly operates as a reception antenna due to the reversibility of the antenna. More specifically, an electromagnetic field induces a magnetic field H, the magnetic field H induces an electric field E perpendicular or substantially perpendicular to the surface of the radiation plate 115, and the electric field E produce a magnetic field H parallel or substantially parallel to the surface of the radiation plate 115, which are coupled to the coupling electrode 125.

The wireless IC device component is functional even if a component on which the wireless IC device component is mounted is made of a metal, and the wireless IC device component similarly operates even if a component on which the wireless IC device component is mounted is an article made of a material other than metal, for example, an electrolyte such as blood, soybean paste, saline solution, or soapy water. When the article on which the wireless IC device component is mounted is a metal or an electrolyte, transmission and reception may be performed from a surface opposite to the surface on which the wireless IC device component is installed because a current passes through the surfaces of the article.

The wireless IC device can preferably use, for example, frequencies within an ultra high frequency (UHF) band (850 MHz to 970 MHz).

As described above, since the resonant frequency of a signal is set by the coupling electrode 125 in the wireless IC device of the first preferred embodiment, the wireless IC device operates as it is even if the wireless IC device is mounted on various articles. Accordingly, variations in the radiation characteristics are prevented or minimized and it is not necessary to change the design of, for example, the radiation plate 115 for each article upon which the wireless IC device is to be mounted. The frequency of a transmission signal radiated from the radiation plate 115 and the frequency of a reception signal to be supplied to the wireless IC chip 5 substantially correspond to the resonant frequency of the coupling electrode 125. Since the frequencies of the transmission and reception signals are determined in the coupling electrode 125, the frequency characteristics do not vary such that stable frequency characteristics are achieved, regardless of the shape, the size, and/or the arrangement relationship of the radiation plate 115, for example, even if the wireless IC device is rounded or is sandwiched between dielectric materials.

Second Preferred Embodiment

A wireless IC device component according to a second preferred embodiment of the present invention preferably includes a coupling electrode 135, as shown in FIGS. 3A and 3B. The coupling electrode 135 preferably includes a pair of coupling portions 136 a and 136 b arranged to be coupled to the wireless IC chip 5 and a pair of opposing ends 136 c and 136 d. The opposing ends 136 c and 136 d are capacitively coupled to each other.

The opposing end 136 c is capacitively coupled to the opposing end 136 d, so that the coupling electrode 135 electrically forms an annular electrode and functions as a magnetic-field antenna. The wireless IC device component functions as a wireless IC device with the coupling electrode 135 being coupled to the radiation plate 115, similarly to the coupling electrode 125 shown in the first preferred embodiment.

The coupling electrode 135 has an inductive reactance (XL: jωL) caused by the electrical length and a capacitive reactance (XC: 1/jωC) caused by the paired opposing ends 136 c and 136 d that are capacitively coupled to each other. Since the inductive reactance has a phase opposite to that of the capacitive reactance, the impedance does not significantly increase because of the increase in the electrical length of the coupling electrode 135. In other words, it is possible to achieve the impedance matching between the wireless IC chip 5 and the radiation plate 115 even if the electrical length of the coupling electrode 135 is increased. Thus, the electrical length of the coupling electrode 135 may be increased to strengthen the magnetic coupling between the coupling electrode 135 and the radiation plate 115.

As in the first preferred embodiment, since the loop surface of the coupling electrode 135 is arranged so as to be perpendicular or substantially perpendicular to the radiation plate 115, the wireless IC device component functions as the wireless IC device even if the wireless IC device component is arranged on the metal surface.

Third Preferred Embodiment

A wireless IC device component according to a third preferred embodiment of the present invention preferably includes a coupling electrode 145 having a U-shape in a side view, as shown in FIG. 4. The coupling electrode 145 is preferably provided from the front surface of a base (not shown) made of resin, for example, to the rear surface thereof and includes an opening 147 and a slit 148 extending to the opening 147 on its surface. The opening 147 and the slit 148 define a pair of coupling portions 146 a and 146 b to be coupled to the wireless IC chip 5. The coupling electrode 145 includes opposing ends 146 c and 146 d. The opposing ends 146 c and 146 d are capacitively coupled to each other.

The opposing end 146 c is capacitively coupled to the opposing end 146 d, so that the coupling electrode 145 electrically forms an annular electrode, functions as a magnetic-field antenna, and is coupled to the radiation plate 115. The operational effects of the third preferred embodiment are similar to those of the second preferred embodiment.

The difference in voltage between the opposing ends 146 c and 146 d is relatively large in the coupling electrode 145 of the third preferred embodiment, such that the opposing end 146 c can be capacitively coupled to the opposing end 146 d even if the opposing end 146 c is a certain distance apart from the opposing end 146 d.

Fourth Preferred Embodiment

A wireless IC device according to a fourth preferred embodiment of the present invention preferably includes the wireless IC chip 5 arranged to process transmission and reception signals having certain frequencies, a radiation plate 15 provided on a base 10, such as a PET film, for example, and a coupling electrode 25 provided on a base 20, such as a PET film, for example, as shown in FIGS. 5A and 5B.

The coupling electrode 25 preferably includes a pair of coupling portions 26 a and 26 b arranged to be coupled to the wireless IC chip 5 and a pair of opposing ends 26 c and 26 d defined by a cutout of the coupling electrode 25. The wireless IC chip 5 preferably includes, for example, a clock circuit, a logic circuit, and a memory circuit. Necessary information is stored in the wireless IC chip 5. A pair of input-output terminal electrodes (not shown) is provided on the rear surface of the wireless IC chip 5. The pair of input-output terminal electrodes is mounted on the pair of coupling portions 26 a and 26 b of the coupling electrode 25 via a conductive adhesive 6 in a manner shown in FIG. 6.

The radiation plate 15 preferably has a dipole shape extending toward both ends in a meandering pattern, for example, and includes a midsection 15 a of the radiation plate 15 is overlapped with the opposing ends 26 c and 26 d of the coupling electrode 25 to be capacitively coupled to the opposing ends 26 c and 26 d. The capacitive coupling between the opposing ends 26 c and 26 d and the radiation plate 15 causes the opposing ends 26 c and 26 d to be electrically connected to each other via the radiation plate 15 and, thus, the coupling electrode 25 defines an annular electrode. The radiation plate 15 and the coupling electrode 25 are each preferably provided by attaching a metal thin film made of a conductive material, such as an aluminum foil or a copper foil, for example, on the bases 10 and 20 to form a pattern, applying a conductive paste made of, for example, Al, Cu, or Ag on the bases 10 and 20, or forming a pattern on a film provided by plating.

The coupling electrode 25 preferably has a certain length from the coupling portions 26 a and 26 b to the opposing ends 26 c and 26 d, has a certain resonant frequency corresponding to the electrical length, and also functions as a matching portion arranged to perform the phase matching. The radiation plate 15 also has a certain resonant frequency corresponding to the electrical length of the radiation plate 15. In addition, the coupling electrode 25 performs the impedance matching between the wireless IC chip 5 and the radiation plate 15.

Accordingly, a transmission signal that is sent from the wireless IC chip 5 and that has a certain frequency is transmitted to the radiation plate 15 via the coupling electrode 25, and a signal having a certain frequency is selected by the coupling electrode 25 from signals received by the radiation plate 15 and the selected signal is supplied to the wireless IC chip 5. Accordingly, in the wireless IC device, the wireless IC chip 5 is operated with the signal received by the radiation plate 15 and the response signal from the wireless IC chip 5 is externally radiated from the radiation plate 15.

In the wireless IC device, the capacitive coupling between the coupling electrode 25 and the radiation plate 15 causes the wireless IC chip 5 to be coupled to the radiation plate 15 to establish the communication between the wireless IC chip 5 and an RFID system in a non-contact manner. Energy is transmitted between the coupling electrode 25 and the radiation plate 15 primarily through the magnetic coupling.

The coupling electrode 25 has an inductive reactance (XL: jωL) caused by the electrical length and a capacitive reactance (XC: 1/jωC) caused by the coupling electrode 25 and the radiation plate 15. Since the inductive reactance has a phase opposite to that of the capacitive reactance, the impedance does not significantly increase because of the increase in the electrical length of the coupling electrode 25. In other words, it is possible to achieve the impedance matching between the wireless IC chip 5 and the radiation plate 15 even if the electrical length of the coupling electrode 25 is increased. The impedance matching is preferably performed by setting a reactance between the wireless IC chip 5 and one terminal of the coupling electrode 25 and also setting a reactance between the other terminal of the coupling electrode 25 and the radiation plate 15 so as to have a complex conjugate relationship.

In other words, since the coupling electrode 25 is capacitively coupled to the radiation plate 15 to provide the capacitive reactance, it is necessary for the coupling electrode 25 to have a relatively larger inductive reactance in order to achieve a certain impedance and the electrical length of the coupling electrode 25 is increased. The longer electrical length causes the coupling electrode 25 to receive an increased amount of magnetic field from the radiation plate 15 and, thus, the magnetic coupling between the coupling electrode 25 and the radiation plate 15 is further strengthened.

In addition, since the coupling electrode 25 is capacitively coupled to the radiation plate 15 via the opposing ends 26 c and 26 d, the mounting accuracy of the coupling electrode 25 on the radiation plate 15 is not strictly limited.

A portion of the signals from the coupling electrode 25 is externally radiated from the wireless IC device as the magnetic field and signals are also externally radiated from the radiation plate 15 as the electric field. Designing the coupling electrode 25 so as to have a resonant frequency lower than the resonant frequency of the radiation plate 15 enables the radiation characteristics to be broadened. The radiation plate 15 is capable of long-range communication by using the electric field and the coupling electrode 25 is capable of short-range communication by using the magnetic field.

In addition, since three sides of the coupling electrode 25 are preferably arranged relatively close to the radiation plate 15 and secondary electromagnetic coupling occurs at the proximity portion, the coupling between the coupling electrode 25 and the radiation plate 15 can be further strengthened. Consequently, it is possible to improve the radiation gain of the wireless IC device and to further broaden the radiation characteristics thereof.

As described above, since the resonant frequency of a signal is set in the coupling electrode 25 in the wireless IC device, the wireless IC device operates properly even if the wireless IC device is mounted on various articles. Accordingly, variations in the radiation characteristics are prevented or minimized and it is not necessary to change the design of, for example, the radiation plate 15 for each article upon which the wireless IC device is to be mounted. The frequency of a transmission signal radiated from the radiation plate 15 and the frequency of a reception signal to be supplied to the wireless IC chip 5 substantially correspond to the resonant frequency of the coupling electrode 25. Since the frequencies of transmission and reception signals are determined in the coupling electrode 25, the frequency characteristics do not vary to achieve stable frequency characteristics, regardless of the shape, the size, and/or the arrangement relationship of the radiation plate 15, for example, even if the wireless IC device is rounded or is sandwiched between dielectric materials.

The shape of the radiation plate 15 is not limited to the dipole shape and a radiation plate 65 having an increased area shown in a sixth preferred embodiment of the present invention described below (refer to FIGS. 14 and 15) may be used. In this case, the base 20 is attached on the radiation plate 65. The radiation plate 65 may be a portion of an article. In addition, the midsection 15 a of the radiation plate 15 may be narrower or wider than the width shown in FIG. 5. Alternatively, the coupling electrode 25 may be shifted leftward or rightward with respect to the central portion of the radiation plate 15.

The coupling electrode 25 may have various shapes including an elliptical or substantially elliptical shape, for example, instead of the rectangular or substantially rectangular shape in the fourth preferred embodiment. For example, the coupling electrode 25 may be bent into multiple portions, for example, as shown in FIG. 7. The same applies to other preferred embodiments of the present invention described herein.

Alternatively, the coupling electrode 25 may be arranged so as to be perpendicular or substantially perpendicular to the radiation plate 15, as shown in FIG. 8, and the pair of opposing ends 26 c and 26 d may be capacitively coupled to the radiation plate 15. The arrangement of the loop surface of the coupling electrode 25 so as to be perpendicular or substantially perpendicular to the radiation plate 15 in the above manner causes a magnetic field parallel or substantially parallel to the radiation plate 15 to be produced. Consequently, an electric field perpendicular or substantially perpendicular to the radiation plate 15 is produced, a magnetic-field loop is induced by the electric-field loop, and this chain expands the electromagnetic-field distribution. As a result, the wireless IC device is functional even if the wireless IC device is arranged on the metal surface. The opposing ends 26 c and 26 d of the coupling electrode 25 may be opposed to the metal surface to be capacitively coupled to the metal surface so as to cause the metal surface to function as the radiation plate 15.

Fifth Preferred Embodiment

The wireless IC chip 5 may preferably be installed on a feed circuit board 1, as shown in FIGS. 9A and 9B. An example in which the wireless IC chip 5 is installed on the feed circuit board 1 is described as a fifth preferred embodiment of the present invention. The radiation plate 15 preferably including the meandering pattern described in the fourth preferred embodiment or the radiation plate 65 having a larger area described below in the sixth preferred embodiment, for example, may preferably be used as the radiation plate, although not shown. The opposing ends of the coupling electrode 25 are capacitively coupled to the radiation plate 15 or 65.

The feed circuit board 1 preferably includes a feed circuit 11 (described in detail below with reference to FIG. 12) including a resonant circuit and/or a matching circuit including inductance elements L1 and L2 that have opposite phases and that are magnetically coupled to each other (denoted by a mutual inductance M), as shown as an equivalent circuit in FIG. 10.

In the wireless IC chip 5, input-output terminal electrodes are preferably electrically connected to one end of a feed terminal electrode 42 a provided on the feed circuit board 1 and to one end of a feed terminal electrode 42 b provided thereon, and mounting terminal electrodes are preferably electrically connected to mounting electrodes 43 a and 43 b via metallic bumps or other suitable structure, for example, as shown in FIG. 11.

The inductance elements L1 and L2 included in the feed circuit 11 have opposite phases and are magnetically coupled to each other to resonate with the frequency processed by the wireless IC chip 5 and to be electromagnetically coupled to the coupling portions 26 a and 26 b of the coupling electrode 25. The feed circuit 11 performs the impedance matching between the wireless IC chip 5 and the radiation plate 15.

Accordingly, preferably, the feed circuit 11 transmits a transmission signal that is sent from the wireless IC chip 5 and that has a certain frequency to the radiation plate 15 via the coupling electrode 25, and the feed circuit 11 selects a signal having a certain frequency from signals that are received by the radiation plate 15 and that are supplied via the coupling electrode 25 and supplies the selected signal to the wireless IC chip 5. Accordingly, in the wireless IC device, the wireless IC chip 5 is operated with the signal received by the radiation plate 15 and the response signal from the wireless IC chip 5 is externally radiated from the radiation plate 15. In other words, the resonant frequency of the feed circuit 11 substantially corresponds to the frequency of a signal transmitted or received via the radiation plate 15.

The effects of the coupling electrode 25 are the same or substantially the same as those described in the fourth preferred embodiment, and the operational effects of the fifth preferred embodiment are similar to those of the fourth preferred embodiment.

The structure of the feed circuit board 1 will now be described with reference to FIG. 12. The feed circuit board 1 is preferably manufactured by stacking, pressure-bonding, and firing ceramic sheets 41 a to 41 h, each of which is made of a dielectric material or a magnetic material, for example. The top sheet 41 a includes the feed terminal electrodes 42 a and 42 b, the mounting electrodes 43 a and 43 b, via-hole conductors 44 a, 44 b, 45 a, and 45 b provided thereon. The second to eight sheets 41 b to 41 h each include line electrodes 46 a and 46 b provided thereon, which define the inductance elements L1 and L2. The second to eighth sheets 41 b to 41 h each include via-hole conductors 47 a, 47 b, 48 a, and 48 b, as required.

Stacking the sheets 41 a to 41 h provides the inductance element L1 in which the line electrodes 46 a are spirally connected via the via-hole conductor 47 a and provides the inductance element L2 in which the line electrodes 46 b are spirally connected via the via-hole conductor 47 b. A capacitance is produced between the line electrodes 46 a and 46 b.

An end 46 a-1 of the line electrode 46 a on the sheet 41 b is connected to the feed terminal electrode 42 a via the via-hole conductor 45 a, and an end 46 a-2 of the line electrode 46 a on the sheet 41 h is connected to the feed terminal electrode 42 b via the via-hole conductors 48 a and 45 b. An end 46 b-1 of the line electrode 46 b on the sheet 41 b is connected to the feed terminal electrode 42 b via the via-hole conductor 44 b, and an end 46 b-2 of the line electrode 46 b on the sheet 41 h is connected to the feed terminal electrode 42 a via the via-hole conductors 48 b and 44 a.

Since the inductance elements L1 and L2 are wound in opposite directions in the feed circuit 11 described above, the magnetic field produced in the inductance element L1 is offset by the magnetic field produced in the inductance element L2. Since the magnetic fields are offset, it is necessary for the line electrodes 46 a and 46 b to have an increased length in order to achieve a desired inductance value. Increasing the length of the line electrodes 46 a and 46 b decreases the Q value so as to eliminate or reduce the steepness of the resonance characteristics, thus broadening the resonant characteristics near the resonant frequency.

The inductance elements L1 and L2 are provided at different leftward and rightward positions in a perspective plan view of the feed circuit board 1. The magnetic fields produced by the inductance elements L1 and L2 have opposite directions. Accordingly, coupling the feed circuit to the coupling portions 26 a and 26 b of the coupling electrode 25 causes currents in opposite directions to be excited in the coupling portions 26 a and 26 b to allow transmission and reception of signals to and from the radiation plate 15 via the coupling electrode 25.

In the fifth preferred embodiment using the feed circuit board 1, the coupling electrode 25 may preferably be provided on the rear surface of the feed circuit board 1, as shown in FIG. 13. In this feed circuit board 1, the coupling electrode 25 is arranged so as to be opposed to the radiation plate 15 or the radiation plate 65 to capacitively couple the opposing ends 26 c and 26 d to the radiation plate 15. Alternatively, the coupling electrode 25 may be arranged so as to be perpendicular or substantially perpendicular to the radiation plate 15 or 65.

The feed circuit board 1 may preferably be a flexible board, for example. The flexible board 1 may be used to attach the board 1 along a curved surface of an article. When the radiation plate 15 is provided as a portion of an article, it is possible to couple the coupling electrode 25 without flexure even if the board 1 is attached along a curved surface of an article because the opposing ends 26 c and 26 d opposing the radiation plate 15 are spaced apart from each other on one surface of the feed circuit board 1.

Sixth Preferred Embodiment

In a wireless IC device according to a sixth preferred embodiment of the present invention, a coupling electrode 55 is provided along surfaces of a flexible dielectric substrate 50 preferably made of polyurethane, for example, which is a wide band, as schematically shown in FIG. 14 and as shown in detail in FIG. 15. The wireless IC chip 5 (or the feed circuit board 1 on which the wireless IC chip 5 is mounted) is preferably mounted on a pair of coupling portions 56 a and 56 b. A pair of opposing portions 56 c and 56 d oppose the broad radiation plate 65 provided on the rear surface of a base 60 preferably made of a dielectric material, for example, to be capacitively coupled to the radiation plate 65. The capacitive coupling between the opposing ends 56 c and 56 d and the radiation plate 65 causes the opposing ends 56 c and 56 d to be electrically connected to each other via the radiation plate 65 and, thus, the coupling electrode 55 defines an annular electrode. As described above in the first preferred embodiment, arranging the loop surface of the coupling electrode 55 so as to be perpendicular or substantially perpendicular to the radiation plate 65 enables the wireless IC device to be arranged on the metal surface. The metal surface may be caused to function as the radiation plate.

In the sixth preferred embodiment, the opposing ends 56 c and 56 d of the coupling electrode 55 oppose the radiation plate 65 via the base 60 preferably made of a dielectric material, for example, to be capacitively coupled to the radiation plate 65. The operational effects of the sixth preferred embodiment are the same or substantially the same as the ones described in the first preferred embodiment. In the sixth preferred embodiment, the base 60 and the radiation plate 65 are not necessarily defined by dedicated components of the wireless IC device and may be defined by portions of an article to which the dielectric substrate 50 of the coupling electrode 55 is attached. The radiation plate 65 may be, for example, a ground electrode of an electric device or an electronic device made of metal. In particular, since the dielectric substrate 50 is flexible and the coupling electrode 55 is separated into left and right portions, the coupling electrode 55 can be easily curved and, thus, can be attached along a curved surface of an article.

In the sixth preferred embodiment, the coupling electrode 55 may preferably be incorporated into the feed circuit board 1 shown in the fifth preferred embodiment, along with the feed circuit 11, as shown in FIG. 16. Alternatively, the coupling electrode 55 may preferably be provided on the rear surface of the feed circuit board 1. When the coupling electrode 55 is incorporated into the feed circuit board 1, the opposing ends 56 c and 56 d of the coupling electrode 55 are capacitively coupled to the radiation plate 65 via the dielectric layers of the board 1. Alternatively, the coupling electrode 55 may be adhered to the radiation plate 65 with a non-conductive adhesive, for example, to capacitively couple the coupling electrode 55 to the radiation plate 65.

Seventh Preferred Embodiment

In a wireless IC device component according to a seventh preferred embodiment of the present invention, a coupling electrode 75 is preferably provided along a flexible dielectric substrate (not shown) made of polyurethane, for example, which is a wide band, as shown in FIGS. 17A and 17B. The wireless IC chip 5 (or the feed circuit board on which the wireless IC chip 5 is mounted) is preferably mounted on a pair of coupling portions 76 a and 76 b. The coupling electrode 75 includes a pair of opposing ends 76 c and 76 d. The opposing ends 76 c and 76 d are overlapped with each other on the rear surface of a base to be capacitively coupled to each other.

The opposing end 76 c is capacitively coupled to the opposing end 76 d, so that the coupling electrode 75 electrically forms an annular electrode and functions as a magnetic-field antenna. The wireless IC device component functions as a wireless IC device with the coupling electrode 75 being coupled to the radiation plate. The operational effects of the seventh preferred embodiment are similar to those of the second preferred embodiment.

As described above in the first preferred embodiment, arranging the loop surface of the coupling electrode 75 so as to be perpendicular or substantially perpendicular to the radiation plate enables the wireless IC device to be arranged on the metal surface. The metal surface may function as the radiation plate.

Eighth Preferred Embodiment

In a wireless IC device component according to an eighth preferred embodiment of the present invention, a coupling electrode 85 is preferably provided along a flexible dielectric substrate 80 from the top surface of the substrate 80 to the bottom surface thereof via left and right end surfaces thereof, as shown in FIG. 18. The coupling electrode 85 has a longitudinal direction and a latitudinal direction in a plan view, and a slit 87 having a flexion is provided at a substantially central portion of the top surface. A pair of coupling portions 86 a and 86 b is preferably opposed to each other in the latitudinal direction at a central portion of the slit 87, and the feed circuit board 1 (refer to FIG. 11 and FIG. 12) on which the wireless IC chip 5 is mounted on the coupling portions 86 a and 86 b. The wireless IC chip 5 is preferably sealed with a resin material 7, for example. The wireless IC chip 5 may be directly mounted on the coupling portions 86 a and 86 b.

In the coupling electrode 85, preferably, a pair of opposing ends 86 c and 86 d is adjacent to a slit 88 at a central portion of the bottom surface of the dielectric substrate 80. In the eighth preferred embodiment, the opposing end 86 c is capacitively coupled to the opposing end 86 d, so that the coupling electrode 85 electrically forms an annular electrode and functions as a magnetic-field antenna. The wireless IC device component functions as a wireless IC device with the coupling electrode 85 being coupled to the radiation plate. The operational effects of the eighth preferred embodiment are similar to those of the seventh preferred embodiment.

In particular, the coupling electrode 85 includes the longitudinal direction and the latitudinal direction in a plan view and the coupling portion 86 a opposes the coupling portion 86 b in the latitudinal direction in the eighth preferred embodiment. Accordingly, even if the coupling electrode 85 is flexed (the flexible dielectric substrate 80 is likely to be flexed in the longitudinal direction), it is possible to prevent the board 1 and the wireless IC chip 5 from being destroyed or separated from one another due to the flexural stress applied to the feed circuit board 1 and the wireless IC chip 5.

Ninth Preferred Embodiment

A wireless IC device component according to a ninth preferred embodiment of the present invention has the same or substantially the same configuration as that of the eighth preferred embodiment, as shown in FIGS. 19A and 19B. The wireless IC device component of the ninth preferred embodiment differs from the wireless IC device component of the eighth preferred embodiment in that the coupling portions 86 a and 86 b are preferably arranged at positions different from those of the pair of opposing ends 86 c and 86 d in a plan view. The wireless IC chip 5 may be directly mounted on the coupling portions 86 a and 86 b or the feed circuit board 1 on which the wireless IC chip 5 is mounted may be mounted on the coupling portions 86 a and 86 b, as shown in the eighth preferred embodiment.

The operational effects of the ninth preferred embodiment are similar to those of the eighth preferred embodiment. Since the opposing ends 86 c and 86 d are defined by a cutout portion of the coupling electrode 85, the dielectric substrate 80 is likely to be bent at this cutout portion. In the ninth preferred embodiment, since the opposing ends 86 c and 86 d are arranged at positions different from those of the coupling portions 86 a and 86 b in a plan view, the bending stress occurring at the opposing ends 86 c and 86 d is prevented from being transmitted to the coupling portions 86 a and 86 b. Accordingly, it is possible to suppress the effect of the bending stress on the wireless IC chip 5 and the feed circuit board 1 mounted on the coupling portions 86 a and 86 b.

Tenth Preferred Embodiment

In a wireless IC device component of a tenth preferred embodiment, a through hole 81 is preferably provided at a substantially central portion of the dielectric substrate 80, the wireless IC chip 5 is disposed in the hole 81, and the wireless IC chip 5 is coupled to the coupling portions 86 a and 86 b bordering on the hole 81, as shown in FIG. 20. The feed circuit board 1 may be mounted in the coupling portions 86 a and 86 b in a state in which the feed circuit board 1 is disposed in the hole 81.

The structure of the coupling electrode 85 in the tenth preferred embodiment is similar to the structure thereof in the ninth preferred embodiment. Accordingly, the operational effects of the tenth preferred embodiment are similar to those of the ninth preferred embodiment. In particular, in the tenth preferred embodiment, since the wireless IC chip 5 is incorporated in the dielectric substrate 80, it is possible to protect the wireless IC chip 5 from an external impact and to reduce the size of the wireless IC device component. In addition, since the opposing ends 86 c and 86 d are preferably arranged at positions different from those of the coupling portions 86 a and 86 b in a plan view, the bottom face side of the hole 81 on which the coupling portions 86 a and 86 b border is sealed with the coupling electrode 85. The hole may be a cavity (a housing portion) having a size sufficient to house the wireless IC chip 5, instead of the through hole.

The wireless IC device component and the wireless IC device according to the present invention are not limited to the preferred embodiments described above, and various changes and modifications may be made to the present invention without departing from the spirit and scope thereof.

For example, the materials of the radiation plate and the base shown in the above preferred embodiments are only examples, and the radiation plate and the base may be made of an arbitrary material as long as the material has necessary characteristics. Processing other than the metal bumping may be used to connect the wireless IC chip to the electrodes.

The wireless IC may be manufactured as an element in the feed circuit board. The provision of the wireless IC in the feed circuit board eliminates parasitic components in the portion in which the wireless IC is connected to the feed circuit to improve the characteristics of the wireless IC device. In addition, the height of the wireless IC device can be reduced. Furthermore, the shape and/or arrangement of the portion at which the feed circuit is coupled to the coupling electrode can be changed to cause the feed circuit to be coupled to the coupling electrode only through the electric field or the magnetic field. The coupling portions may not be defined by a pair of ends and may be linear portions as long as the wireless IC or the feed circuit can be coupled to the coupling portions. The pair of opposing ends of the coupling electrode or the opposing ends opposing the radiation plate may be capacitively coupled to each other via another electrode.

As described above, preferred embodiments of the present invention are useful for the wireless IC device components and the wireless IC devices and, in particular, preferred embodiments of the present invention are excellent in that the coupling electrode can be more satisfactorily coupled to the radiation plate.

While preferred embodiments of the present invention have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present invention. The scope of the present invention, therefore, is to be determined solely by the following claims. 

What is claimed is:
 1. A wireless IC device comprising: a wireless IC; a coupling electrode including at least one coupling portion arranged to be coupled to the wireless IC directly or via a feed circuit and a pair of ends arranged opposite to each other so as to define an annular electrode including an opening portion defined by an inner edge of the annular electrode; and a radiation plate coupled to the coupling electrode; wherein a main surface of the annular electrode is parallel or substantially parallel to a main surface of the radiation plate; each of the pair of ends of the annular electrode is overlapped with a portion of the radiation plate in a plan view and coupled to the portion of the radiation plate via a capacitive coupling; and a majority of the opening portion is not overlapped with the radiation plate in the plan view.
 2. The wireless IC device according to claim 1, wherein the annular electrode is coupled to the radiation plate via a magnetic coupling.
 3. The wireless IC device according to claim 2, wherein a first group of signals of a plurality of signals are externally radiated from the coupling electrode via a magnetic field, and a second group of signals of the plurality of signals are externally radiated from the radiation plate via an electric field.
 4. The wireless IC device according to claim 3, wherein a resonant frequency of the coupling electrode is lower than a resonant frequency of the radiation plate.
 5. The wireless IC device according to claim 1, wherein the at least one coupling portion of the coupling electrode is not overlapped with the radiation plate in the plan view.
 6. The wireless IC device according to claim 1, wherein the pair of ends of the coupling electrode is coupled to a central portion of the radiation plate.
 7. The wireless IC device according to claim 1, wherein the radiation plate is defined by a portion of an article to which the wireless IC device is attached. 